1. Technical Field
The present disclosure relates to an electrosurgical forceps, and, more particularly, the present disclosure relates to an endoscopic electrosurgical forceps for sealing and/or cutting large tissue structures.
2. Background of Related Art
Electrosurgical forceps utilize both mechanical clamping action and electrical energy to affect hemostasis by heating the tissue and blood vessels to coagulate, cauterize and/or seal tissue. Many surgical procedures require cutting and/or ligating large blood vessels and large tissue structures. Due to the inherent spatial considerations of the surgical cavity, surgeons often have difficulty suturing vessels or performing other traditional methods of controlling bleeding, e.g., clamping and/or tying-off transected blood vessels or tissue. By utilizing an elongated electrosurgical forceps, a surgeon can either cauterize, coagulate/desiccate, dissect, and/or simply reduce or slow bleeding simply by controlling the intensity, frequency and duration of the electrosurgical energy applied through the jaw members to the tissue. Most small blood vessels, i.e., in the range below two millimeters in diameter, can often be closed using standard electrosurgical instruments and techniques. However, larger vessels can be more difficult to close using these standard techniques.
In order to resolve many of the known issues described above and other issues relevant to cauterization and coagulation, a technology was developed by Valleylab, Inc. of Boulder, Colo., a division of Tyco Healthcare LP (now Covidien—Energy Based Devices) called vessel or tissue sealing. The process of coagulating vessels is fundamentally different than electrosurgical vessel sealing. For the purposes herein, “coagulation” is defined as a process of desiccating tissue wherein the tissue cells are ruptured and dried. “Vessel sealing” or “tissue sealing” is defined as the process of liquefying the collagen in the tissue so that it reforms into a fused mass with limited demarcation between opposing tissue structures. Coagulation of small vessels is sufficient to permanently close them, while larger vessels and tissue need to be sealed to assure permanent closure.
In order to effectively seal larger vessels (or tissue) two predominant mechanical parameters are accurately controlled—the pressure applied to the vessel (tissue) and the gap distance between the electrodes—both of which are affected by the thickness of the sealed vessel. More particularly, accurate application of pressure is important to oppose the walls of the vessel; to reduce the tissue impedance to a low enough value that allows enough electrosurgical energy through the tissue; to overcome the forces of expansion during tissue heating; and to contribute to the end tissue thickness which is an indication of a good seal.
Providing an instrument which consistently provides the appropriate closure force between opposing electrode within a preferred pressure range will enhance the chances of a successful seal. It has been found that the pressure range for assuring a consistent and effective seal for large vessels and tissue structures is between about 3 kg/cm2 to about 16 kg/cm2 and, desirably, within a working range of 7 kg/cm2 to 13 kg/cm2. As can be appreciated, manufacturing an instrument which is capable of consistently providing a closure pressure within these working ranges is quite a design challenge for instrument manufacturers.
It may be necessary for a surgeon to perform both vessel sealing and dissection during certain surgical procedures. In such procedures, a greater number of instruments may be required to achieve the surgical objective. The use of greater numbers of instruments may affect surgical outcomes, due in part to the need to perform instrument changes in which additional time is used to withdraw one instrument, to prepare a subsequent instrument for use, and to manipulate the subsequent instrument into position for performing the required surgical steps.